Islet neogenesis gene associated protein (INGAP protein) has been identified as a pancreatic acinar cell protein that can induce islet cell neogenesis from progenitor cells resident in the pancreas in a manner that recapitulates islet development during normal embryogenesis. INGAP is unique in its ability to stimulate growth and differentiation of islets of Langerhans from precursor cells associated with pancreas. These islets evolve a mature insulin secretory profile capable of responding to perturbations in blood glucose in a physiologic manner. This potential anti-diabetic therapeutic has been shown to demonstrate homology across several species and to exert a biological response.
Pancreatic islet cell mass is lost in type 1 diabetes mellitus, a disease in which a progressive autoimmune reaction results in the selective destruction of insulin-producing β-cells. In type 2 diabetes mellitus, so-called adult-onset disease, but also increasingly a condition in young overweight people, the β-cell mass may be reduced by as much as 60% of normal. The number of functioning β-cells in the pancreas is of critical significance for the development, course, and outcome of diabetes. In type I diabetes, there is a reduction of β-cell mass to less than 2% of normal. Even in the face of severe insulin resistance as occurs in type II diabetes, the development of diabetes only occurs if there is inadequate compensatory increase in β-cell mass. Thus, the development of either of the major forms of diabetes can be regarded as a failure of adaptive β-cell growth and a subsequent deficiency in insulin secretion. Stimulating the growth of islets and β-cells from precursor cells, known as islet neogenesis, is an attractive approach to the amelioration of diabetes. There is need in the art for methods to identify agents that can modulate the expression of INGAP, whether in animals or in cultured cells.